Winter drought stress can delay flowering, prevent fruit loss in orange crops

Sep 20, 2010
Researchers found ways to extend late-season harvest of popular Florida 'Valencia' oranges. Credit: Photo by Juan Carlos Melgar.

Successful mechanical harvesting of perennial fruit crops requires efficient, economical harvesting systems that do not reduce trees' production life or diminish fruit quality. Most of the world's citrus is now harvested manually, but the use of efficient and lower-cost mechanical harvesting techniques is expected to increase in the next few years, especially in the large citrus plantations in Florida and Brazil. The citrus industry is ramping up efforts to extend the harvest season past June, when the following year's crop becomes large enough to be susceptible to mechanical harvesting; discovering techniques that improve late-season harvesting will give growers better tools to minimize damaging impacts on the next year's fruit yield.

Researchers from the University of Florida's Citrus Research and Education Center published a study in a recent issue of that determined if winter could successfully delay flowering and fruit development of immature 'Valencia' sweet oranges to avoid young fruit loss during late-season mechanical harvesting.

The researchers hypothesized that if the Florida 'Valencia' bloom period could be delayed by a few weeks using winter drought stress—without negative effects on the quality of the current season's crop—the "fruitlets" from delayed flowering would be too small to be affected by mechanical harvesting late in the current harvest season, thus safely extending the mechanical harvesting period.

The study was designed by Juan Carlos Melgar, Jill M. Dunlop, L. Gene Albrigo, and James P. Syvertsen and conducted at the Citrus Research and Education Center in Lake Alfred. Beginning in December 2006 and continuing for three consecutive seasons, Tyvek® water-resistive barrier material was used as a rain shield groundcover under 13-year-old-trees. The researchers applied three treatments: drought (no irrigation and covered soil), rain only (no irrigation, no cover), and normal irrigation (rain and no cover). Covers were removed in February or March and normal irrigation and fertilization were resumed.

The drought stress did not affect fruit yield, size, percentage juice, or juice quality of the current crop harvested in May and June relative to continuously irrigated trees. Drought stress delayed flowering by 2 to 4 weeks so that the immature fruit for next season's crop were smaller than on continuously irrigated trees during June, but fruit growth caught up by September. During mechanical harvesting, previously drought-stressed trees lost fewer young fruit than continuously irrigated trees.

"The results showed that winter drought stress effectively delayed flowering and avoided young fruit loss during late-season mechanical harvesting without negative impacts on yield or fruit quality", Melgar noted.

The researchers observed that rain-excluding covers were used as an experimental tool, but that the covers may not be a viable commercial option for growers. They added that natural cover crops may help in inducing drought stress, but are yet to be tested as a management tool.

Explore further: High-quality drug testing helps protect the integrity of California horse racing

More information: The complete study and abstract are available on the ASHS HortScience electronic journal web site: hortsci.ashspublications.org/c… nt/abstract/45/2/271

Provided by American Society for Horticultural Science

not rated yet
add to favorites email to friend print save as pdf

Related Stories

Reclaimed wastewater benefits Florida's citrus orchards

Jul 17, 2008

The Sunshine State has seen rapid growth in population during the last 50 years. The 1997 U.S. Census showed that the population of Florida increased more than five-and-a-half times from 1950 to 2000. Naturally, ...

New Farming Wrinkle May Help Peanut Growers

Jan 15, 2010

(PhysOrg.com) -- Using a combination of conservation tillage and deficit irrigation management in peanut production can promote conservation of water during the early growing season without hurting yields, ...

Protecting wine grapes from heat and drought

Feb 17, 2009

Deficit irrigation is an agricultural technique used to achieve a variety of results depending on the crop. For white wine grapes, it balances the crop load by limiting the canopy size so there aren't too ...

New management methods extend blackberry season

Dec 11, 2009

Fruit growers' profits have traditionally been limited by the seasons, particularly in colder climates where growing seasons can be short. Thanks to researchers and fruit breeders, newly developed varieties ...

Recommended for you

Himalayan Viagra fuels caterpillar fungus gold rush

10 hours ago

Overwhelmed by speculators trying to cash-in on a prized medicinal fungus known as Himalayan Viagra, two isolated Tibetan communities have managed to do at the local level what world leaders often fail to ...

Science casts light on sex in the orchard

13 hours ago

Persimmons are among the small club of plants with separate sexes—individual trees are either male or female. Now scientists at the University of California, Davis, and Kyoto University in Japan have discovered ...

Researchers capture picture of microRNA in action

13 hours ago

Biologists at The Scripps Research Institute (TSRI) have described the atomic-level workings of "microRNA" molecules, which control the expression of genes in all animals and plants.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.